Dry barrel finishing machine

Abstract: An improved dry barrel finishing machine in which a mass consisting of media (30) and workpieces is caused to flow in the barrel (1) of the machine for abrasive finishing of the workpieces and in which air suction is used to remove dust resulting from the finishing operation and to cool the barrel and the mass. The mass is caused to flow by rotation of the barrel by a motor (22) or through the vibration of the barrel by a driving mechanism (40;61). Air outlets (12,24) are provided in the barrel. An air suction device (23) draws air through the barrel and around the workpieces and media during the finishing operation. The drawn out air picks up dust and media particles resulting from the abrasive finishing operation and cools the media and the barrel.

Description: This invention relates to a dry barrel finishing machine and a method of dry barrel finishing, wherein finishing media and workpieces are caused to flow in the barrel of the machine for fine abrasive finishing of the workpieces. Generally, barrel finishing is well known as a method for finely grinding workpieces such as bolts, shafts, bearings, etc. In barrel finishing, a mass, which is comprised of finishing media and workpieces, is charged into a receptacle, i.e. a barrel, and the barrel is activated to cause the mass to flow in it so as to finish the workpieces through interactive attrition between the workpieces and the media. Barrel finishing includes dry finishing and wet finishing. Wet finishing uses compounds and water as well as finishing media, while dry finishing does not use fluid. Wet barrel finishing requires washing and drying of the workpieces after the finishing, as well as water treatment for removing waste attrition fluid and waste washing water. It is well known that a drawback of wet barrel finishing is that it requires a drying apparatus and a fluid treatment device, and therefore it requires more space for these items. Another drawback is that wet barrel finishing takes additional time and labor. In view of such drawbacks, dry barrel finishing is often used. In dry barrel finishing, however, attrition produces dust and fragments of the media. Further, frictional heat is generated due to the attrition between the workpieces and the media, and between the barrel and the mass. The attrition dust tends to spread out of the barrel and contaminate the environment. The dust also causes clogging in the media, thereby lowering the abrasive ability of the media and resulting in uneven finishing on the workpieces. Further, in a conventional centrifugal barrel finishing machine, which has an upper stationary tank and a bottom rotary disc, fragments of the media tend to get caught in the space or slit between the rotary disc and the stationary tank. If any fragment becomes jammed in the slit, the rotating disc and the tank are heavily rubbed thereby, and a frictional heat of high temperature will be generated. This heat tends to melt any liners covering the surfaces of the disc and the tank, and as a result, fragments adhere to these liners, thereby hindering the rotation of the disc. Recently, artificial plastic media have been used in barrel finishing. This plastic medium is generally produced by externally heating, in a mold, a mixture of abrasive material and grains of bonding material of an unsaturated polyester resin, a polyvinyl chloride resin, etc. Through this external heating, if the entire mixture is sufficiently heated, a skin layer of the bonding material is formed on the outside of the medium. If on the other hand the mixture is heated such that only the outside of the medium is heated, so as to prevent such a skin layer on the surface of the medium, the inner part of the medium will be brittle because the abrasive material and the bonding material have not been combined sufficiently. These resulting brittle media will cause fragments to appear during barrel finishing, and the fragments may be jammed in the slit of the barrel as described above. Japanese Patent (Y) 2-43,652 discloses an improved plastic finishing medium which is, for example, in the shape of a cylinder. This medium is porous and has no skin layer on the outer surface. It contains abrasive grains combined with the bonding material and has pores between the abrasive grains. Since the abrasive grains are separated by pores and are always exposed, they are effective. DE-A-36 23 869 discloses a dry barrel finishing machine, comprising: a base; a barrel mounted on the base for receiving a mass consisting of finishing media and workpieces; driving means for causing the mass to flow in the barrel; air suction means connected to the barrel; and a dust collector connected to the air suction means for receiving air with attrition dust therein from the air suction means. The present invention, according to one aspect thereof, is characterised over the disclosure of DE-A-36 23 869 in that the barrel includes: a stationary hollow cylindrical tank; a supporting plate mounted on the base for supporting said tank; and a rotary plate mounted on the base so as to be located above and spaced apart from said supporting plate, said rotary plate forming with said supporting plate a passage, said rotary plate further forming with said tank the barrel and a slit around the bottom of the barrel for the air from the barrel to flow to the air suction means. The present invention provides a dry barrel finishing machine equipped with an air suction device and a dust collector for causing air to flow through the barrel and remove the attrition dust produced during barrel finishing. The air flow also reduces the frictional heat evolution of the mass and the barrel. According to a further aspect of the invention there is provided a method of dry barrel finishing, comprising the steps of: charging into an open barrel a mass consisting of a predetermined amount of workpieces and finishing media ; causing the mass to flow in the barrel; sucking air into the open barrel while the mass is flowing so that air passes through the mass; and discharging the air together with the attrition dust borne in the air, characterised in that the barrel comprises a stationary hollow cylindrical tank, a supporting plate for supporting said tank, and a rotary plate located above and spaced apart from said supporting plate, said rotary plate forming with said supporting plate a passage and forming with said tank a slit through which the barrel communicates with said passage. Using a medium which is porous and has no outer skin layer of bonding material is preferable for the purpose of dry barrel finishing. In the accompanying drawings:- Fig. 1 is a partially sectional front view of a first embodiment of a dry barrel finishing machine according to the present invention; Fig. 2 is a plan view of the machine of Fig. 1; and Fig. 3 is a partially sectional front view of a medium for use in barrel finishing machines of this invention. In Figs. 1 and 2, a dry barrel finishing machine has a centrifugal barrel 1. The barrel 1 is mounted between a pair of portal frames 2,2 which serve as a base for the barrel. The barrel 1 accommodates workpieces and finishing media and causes them to flow in it for the abrasive finishing of the workpieces. The barrel 1 includes a fixed cylindrical tank 4, a disc-shaped plate or dish 5 for supporting the tank 4, and a bottom rotary plate 9. A liner 3 is attached to the inner surface of the cylindrical tank 4. The supporting plate 5 is integrally mounted on a cylindrical boss 6. The rotary plate 9 is disposed above the supporting plate 5 and is fixed by fasteners, such as bolts, to a vertical shaft 8 which is positioned within the boss 6 and is mounted rotatably to the boss 6 via bearings 7,7 for the smooth rotation of the shaft 8. As shown in Fig. 1, the circumferential edge and the upper surface of a part of the rotary plate 9 are covered by a liner 11 so that there is a circular slit 12 between the liner 11 on the edge of the rotary plate 9 and the liner 3 on the lower portion of the cylindrical tank 4. The width of the slit is so small that the media and workpieces cannot enter it. A space 10 between the supporting plate 5 and the bottom rotary plate 9 communicates through the slit 12 with a space above the rotary plate 9 so that air entraining any attrition dust can flow between the spaces. A driving unit 20 is attached to the boss 6 and is operatively coupled to the vertical shaft 8 for rotating the bottom rotary plate 9 about the axis of the vertical shaft 8. The unit 20 includes, in this example, reduction gears 21 and a motor 22 for driving the reduction gears 21. As clearly shown in Fig. 2, the supporting plate 5 at both sides (the top and the bottom in Fig. 2) is provided with a pair of arms 13, 13 which are connected to shafts 14, 14. The shafts 14, 14 are rotatably supported on bearings 15, 15 mounted on the frames 2, 2. Thus, the barrel 1 including the tank 4 and plates 5, 9, the boss 6, the vertical shaft 8 in the boss, and the driving unit 20 are supported by the frames 2, 2 through the shaft 14, 14. A sprocket wheel 16 is attached to one of the shafts 14, 14. A motor 17 is mounted on the frames 2, 2 at a lower portion, and a sprocket wheel 18 is attached to the output shaft of the motor 17. A chain belt 19 is engaged with the wheels 16, 18. Thus, the motor 17 is operatively coupled to the barrel 1. Therefore, the barrel turns about the axis of the arms 13, 13 when the motor 17 operates. An air suction device 23 is disposed under the supporting plate 5. The device 23 includes a suction hole 24 formed in the bottom portion of the supporting plate 5, and a flexible duct 25. One end of the flexible duct 25 is connected to the suction hole 24, and the other end is connected to a dust collector 26. The dust collector may be installed on the floor or any other suitable place and is connected to a vacuum source (not shown). In Fig. 3, a finishing medium piece 30 is shown. This medium piece 30 is as disclosed in the above-mentioned Japanese Patent (Y) 2-43,652 and is suitable for use in dry barrel finishing machine according to the present invention. To produce the medium pieces 30, a mixture comprised of a certain amount of abrasive grains 30a and of plastic grains 30b for bonding the abrasive grains 30a is dropped into a mold. The abrasive grains 30a may be ceramics containing any zirconium oxide grains, aluminum oxide grains, silicon carbide grains, titania grains, etc. of mesh size 60-1500. The plastic grains 30b may be selected from the group of a phenolic resin, urea resin, melamine resin, epoxy resin, etc., of which the dielectric loss factor (10 c/s - 10 6 c/s) is more than 0.02. The mold may be, for example, made of a silicon gum, of which the dielectric loss factor (10 c/s - 10 6 c/s) is more than 0.02. The mixture in the mold is then compressed. After compression, the mixture is heated for 0.5-3 minutes by a high-frequency heater so that the resin 30b is melted and the abrasive grains bonded completely. The medium piece 30 thus produced is porous because it contains small pores 30b which are evenly spread in the cylindrical body. Therefore, the medium piece is not covered with a skin layer of resin, and abrasive grains 30a are exposed. When the medium is rubbed against workpieces during the finishing operation, the abrasive grains 30a are always exposed. Now, the operation of this dry barrel finishing machine will be explained. The barrel 1 is kept horizontal, and a suitable amount of workpieces and media are placed in the barrel. Then, the motor 22 of the driving unit 20 is operated to transmit the driving power through the reduction gears 21 and the vertical shaft 8, thereby causing the rotary plate 9 to rotate horizontally. The mass consisting of the media and the workpieces advances along the inner surface of the tank 4 by taking a spiral motion as shown by exemplary lines 29 in Fig. 1. During the finishing process, the workpieces can be effectively finished since the abrasive grains 30a, which serve as effective blades, are always exposed when the media 30 pieces are worn. Since the vacuum source and dust collector 26 are activated during finishing, air above the tank 4 is caused to flow in the direction shown by 27 and through the circular slit 12, the space 10, and the duct 25 into the dust-collecting device 26. This air flow prevents the attrition dust produced during barrel finishing from spreading out upwardly from the tank 4. The attrition dust becomes entrained in the air and guided into the dust collector 26. The dust in the device 26 may be disposed of subsequently. This air flow, which passes through the tank 4, also serves to lower the frictional heat of the mass and the barrel caused during the abrasive finishing. After the finishing is completed, motor 17 is operated to rotate the barrel 1 about the axis of the horizontal arms so that the mass in the barrel is discharged from the opening of the tank 4. The barrel is then returned to the original position. Although the machine does not require any cover for the tank 4, a simple tank cover having apertures in it may be provided, if desired. In any case, the top of the barrel must be open to air to cause an air flow in the barrel. In the embodiment shown in the drawings, the mass can be discharged easily from the top of the barrel. Further, since all elements for the operation of the barrel 1 are disposed in the frames 2, 2 thereunder, the machine can be compact.

Claims: A dry barrel finishing machine, comprising: a base (2); a barrel (1) mounted on the base for receiving a mass consisting of finishing media (30) and workpieces; driving means (20) for causing the mass to flow in the barrel; air suction means (23) connected to the barrel; and a dust collector (26) connected to the air suction means for receiving air with attrition dust therein from the air suction means, characterised in that the barrel includes: a stationary hollow cylindrical tank (4); a supporting plate (5) mounted on the base (2) for supporting said tank; and a rotary plate (9) mounted on the base so as to be located above and spaced apart from said supporting plate, said rotary plate forming with said supporting plate a passage (10), said rotary plate further forming with said tank the barrel (1) and a slit (12) around the bottom of the barrel for the air from the barrel to flow to the air suction means (23). A machine as claimed in claim 1, wherein the inner surface of said tank (4) and the upper surface of said rotary plate (9) are covered with liners (3,11). A machine as claimed in claim 1 or 2, wherein the said driving means comprises a motor (22) mounted under the said supporting plate (5) for rotating the rotary plate (9) to cause the mass to flow in the barrel. A machine as claimed in any preceding claim, wherein the said air suction means (23) includes a suction hole (24) formed in the said supporting plate (5), the hole being open to the said passage (10), and a duct (25) connected at one end to the said hole and at the other end to the said dust collector (26). A machine as claimed in any preceding claims, wherein the said supporting plate (5) is rotatably mounted on the base (2) so as to be turnable about a horizontal axis. A method of dry barrel finishing, comprising the steps of: charging into an open barrel (1) a mass consisting of a predetermined amount of workpieces and finishing media (30); causing the mass to flow in the barrel; sucking air into the open barrel while the mass is flowing so that air passes through the mass; and discharging the air together with the attrition dust borne in the air, characterised in that the barrel comprises a stationary hollow cylindrical tank (4), a supporting plate (5) for supporting said tank (4), and a rotary plate (9) located above and spaced apart from said supporting plate (5), said rotary plate forming with said supporting plate (5) a passage (10) and forming with said tank a slit (12) through which the barrel (1) communicates with said passage (10). A method as claimed in claim 6, wherein the air in the barrel is sucked from a lower part of the barrel.

Inventors: ISHIDA TAKAO, KOHKETSU YOSHINORI, NISHIMURA KAZUTOSHI, ISHIDA, TAKAO, KOHKETSU, YOSHINORI, NISHIMURA, KAZUTOSHI
Applicants: SINTOBRATOR LTD, SINTOBRATOR, LTD.
Application year: 1994
Main classification: B24B31
IPC codes: B24B31